3444 Abstract. – OBJECTIVE: It was hypothe- sized that activity exercise at professional lev- els could lead to an increase in metabolic lev- els and a decrease in performance parameters. These trends are explained by physical activity as a cellular stressor. SUBJECTS AND METHODS: We used an al- gorithm, Laboratory Index which evaluates sal- ivary cortisol, CK and d-ROMs, collected pre- viously from elite Italian soccer players, com- pared to InStat Index. The last one estimates an- alytically the athlete’s performance in soccer pitch, applying the Heath Maps. RESULTS: A good agreement between the two Index was obtained, especially for two players, who showed an ideal combined trend. CONCLUSIONS: We would investigate the clinical and activity profle of soccer players with the aim of providing information for the de- velopment of training strategies. Also, the per- formances, during training and match time, are an objective evaluation of the athlete’s physi - cal preparation. As a consequence, the combi- nation of two Index could be used for a new ap- proach to the sports world. Key Words: Athletic performance, Laboratory Index, InStat In- dex, Cellular stress, Oxidative stress, Reactive Oxygen Species, Physical exercise. Introduction Physical exercise strongly affects human me- tabolism and causes biochemical changes. This is refected in the results of laboratory analyses of changes in serum parameters, which indicate degrees of fatigue. The many faces of different types of training and the variety of physiological reactions of trainees explain why sport medicine is still looking for a perfect way to monitor the effects of training 1 . Muscle metabolism parameters, like creatine kinase (CK), derivates of reactive oxygen me- tabolites (d-ROMs) and salivary cortisol, are usually increased after exercise. Creatine ki- nase (CK) is an enzyme present mainly in skel- etal muscle and heart muscle. An elevated cre- atine kinase value may be due to heterogeneous causes, including muscle fatigue following in- tense sports training. CK is a dimeric globular protein consisting of two subunits with a molec- ular mass of 43 kDa. It buffers cellular ATP and ADP concentrations by catalysing the revers- ible exchange of high-energy phosphate bonds between phosphocreatine and ADP produced during contraction 2 . The serum level of skeletal muscle enzymes is a marker of the functional status of muscle tissue and varies widely in European Review for Medical and Pharmacological Sciences 2021; 25: 3444-3452 M. PIERI 1,2,3 , M.A. PERRONE 4,5 , A. IMBROGNO 6 , F. TOMASSETTI 2,7 , R. COLOMBO 2 , L. LEONE 8 , S. AGUZZETTI 2 , S. TECCE 2 , G. MERRA 9 , A. BERNARDINI 10 , G. CALUGI 2 1 Department of Experimental Medicine, University of Tor Vergata, Rome, Italy 2 Lifebrain srl, Rome, Italy 3 Clinical Biochemistry, Tor Vergata University Hospital, Rome, Italy 4 Department of Cardiology, University of Tor Vergata, Rome, Italy 5 University Sports Centre, University of Rome Tor Vergata, Rome, Italy 6 Department of System Medicine, University of Tor Vergata, Rome, Italy 7 Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy 8 Lifebrain Lecce, Lecce, Italy 9 Department of Biomedicine and Prevention, University of Rome Tor Vergata, Italy 10 Departement of Industrial Engineering University of Tor Vergata, Rome, Italy Corresponding Author: Massimo Pieri, MD; e-mail: massimo.pieri@uniroma2.it Influence of Laboratory Index on match performance. A comparison study to evaluate physical performance in professional soccer players of an Italian Elite Team